1. Field of the Invention
The present invention relates to an inflating-type safety system for a motor vehicle, more specifically to a hybrid inflator capable of inflating an air bag rapidly and reliably regardless of an environmental temperature in a practical use and to an air bag apparatus using the hybrid inflator.
2. Description of Related Art
With the development of an inflator for an inflating-type safety system of motor vehicles, a hybrid inflator using both a pressurized gas and a solid gas generating agent has been attracting attention. A main design requirement for a hybrid inflator is that the inflator inflates an air bag to a predetermined amount in a predetermined time so that the air bag is effectively activated. Various proposals concerning a structure to meet the requirement have heretofore been made, where the art disclosed in JP-A No. 10-100851 and the like have been known as prior art.
An object of the present invention is to provide a hybrid inflator capable of inflating an air bag rapidly and reliably and has a high safety, and to provide an air bag apparatus using such a hybrid inflator.
The present invention provides, as one means for solving the above problem, a hybrid inflator for an inflating-type safety system of a vehicle provided with an air bag, which comprises an inflator housing filled with a pressurized medium, a gas generator stored in the inflator housing and provided with at least one gas generating chamber containing gas generating means, and ignition means jointed to the gas generator, wherein a flow-passage, through which the pressurized medium flows at the time of activation of the hybrid inflator, is closed on the midway by a main rupturable plate, and a plurality of nozzles for controlling the amount of outflow of the pressurized medium and combustion gas are provided at the passage, through which the pressurized medium flows.
Incidentally, in the present invention, the passage, through which the pressurized medium flows at the time of activation of the hybrid inflator, can be set properly or modified according to the structure of the hybrid inflator.
The present invention is structured such that a change in an internal pressure inside the hybrid inflator is controlled by controlling the amount of outflow of the pressurized medium and the combustion gas according to function of a plurality of the nozzles provided at the passage through which the pressurized medium flows, and in case that the present invention is applied to an air bag system, the air bag can be inflated rapidly and reliably without influence of an environmental temperature in practical use.
Furthermore, the hybrid inflator of the present invention can be structured such that a plurality of the nozzles for controlling the amount of outflow of the pressurized medium and the combustion gas are provided at a flow-passage of the pressurized medium upstream of the main rupturable plate.
Thus, in a case that a plurality of the nozzles are provided at the flow-passage upstream of the main rupturable plate, for example, a hybrid inflator with the following respective structures may be provided.
One structure can be that a portion upstream of the main rupturable plate of the flow-passage for the pressurized medium is formed of a cylindrical member, one end side of the cylindrical member faces the main rupturable plate while the other end side thereof is closed, and a plurality of the nozzles comprising through-holes are provided in a side wall of the cylindrical member.
Other structure can be that a portion upstream of the main rupturable plate of the flow-passage for the pressurized medium is formed of a cylindrical member, one end side of the cylindrical member faces the main rupturable plate, and the other side thereof is provided with a plurality of the nozzles comprising through-holes. In this case, no nozzle is provided in a side wall of the cylindrical member.
Still other structure can be that a portion upstream of the main rupturable plate of the pressurized medium is formed of a cylindrical member, one end side of the cylindrical member faces the main rupturable plate, and the other end side and a side wall are provided with a plurality of the nozzles comprising through-holes.
Also, the hybrid inflator of the present invention can be structured such that a plurality of the nozzles for controlling the amount of outflow of the pressurized medium and the combustion gas are provided downstream of the main rupturable plate of the flow-passage for the pressurized medium.
Thus, in a case that a plurality of the nozzles is provided in the flow-passage downstream of the main rupturable plate, such a structure can be employed that a portion downstream of the main rupturable plate of the flow-passage is formed of a cylindrical member, one end side of the cylindrical member faces the main rupturable plate and the other end side and/or the side wall are provided with a plurality of the nozzles comprising through-holes. For example, a plurality of discharging ports for the pressurized medium and the combustion gas from the hybrid inflator, which is positioned downstream of the main rupturable plate of the flow-passage can be constituted as nozzles.
In the hybrid inflator of the present invention, nozzles may be provided upstream of the main rupturable plate of the flow-passage or downstream of the main rupturable plate of the flow-passage or at both the portions, but it is preferable that the nozzle is provided at the portion upstream of the main rupturable plate of the flow-passage.
In the present invention, respective opening areas of a plurality of the nozzles may be made equal to one another, or they may be made different from one another. The opening area of the nozzle is set such that the amount of outflow of the pressurized medium and the combustion gas can be controlled to a desired degree according to the performance and application required for the hybrid inflator. Since the opening area of the nozzle corresponds to a nozzle diameter, when it is expressed by the nozzle diameter, the nozzle diameter may preferably be 1 to 8 mm, more preferably 1 to 6 mm.
Also, the total opening area of a plurality of the nozzles may preferably be 40 to 120 mm2, more preferably 60 to 90 mm2, and the number of nozzles should be determined in relation to the total opening are of the nozzles, and it may be preferably 2 to 8, more preferably 4 to 6.
Thus, by adjusting the opening areas of a plurality of the nozzles or the total area thereof, control on the amount of outflow of the pressurized medium and the combustion gas and control on the change in the internal pressure of the hybrid inflator can be performed more easily.
In the present invention, such a structure can be employed that a plurality of the nozzles are closed by shielding means, and a closed state by this shielding means is selected according to the position where a plurality of the nozzles are provided. When a plurality of the nozzles are provided in the flow-passage upstream of the main rupturable plate, such a structure can be employed that part of a plurality of the nozzles are closed by the shielding means (that is, a state such that shielded nozzles and opened nozzles exist). When a plurality of the nozzles are provided in the flow-passage downstream of the main rupturable plate, such a structure can be employed that part or all of a plurality of the nozzles are closed by the shielding means.
This shielding means is ruptured according to increase in internal pressure of the hybrid inflator at the activation thereof. When all of a plurality of the nozzles are closed by the shielding means, it is preferable that pressures required to rupture the respective shielding means are different. For example, in a case that there are six nozzles, breaking pressures of the respective shielding means can be made different one by one or by grouping two or three. The pressure by which the shielding means is broken can be adjusted by changing the diameter of the nozzle, the strength (thickness, material or the like) of the shielding means, or the like.
By changing the pressure required to rupture the shielding means variously, rupturing easiness (i.e., long/short in rupturing time) of the shielding means can be changed in a group of nozzles, so that the amount of outflow of the pressurized medium and the combustion gas can be controlled.
By closing the nozzles by the shielding means in this manner, the control on the amount of outflow of the pressurized medium and the combustion gas and the control on change of the internal pressure in the hybrid inflator can be made easier. That is, since by burning a gas generating means to generate a combustion gas with a high temperature, the internal pressure in the hybrid inflator is gradually increased, the shielding means is ruptured according to the increase in the internal pressure so that the total opening area of the nozzles is changed in a stepwise manner. Therefore, the amount of outflow of the pressurized medium and the combustion gas can be controlled so that the change of the internal pressure in the hybrid inflator can be controlled. Thereby, particularly, a desirable pressure curve such as shown in FIG. 3 can be obtained.
The strength of the shielding means used in the present invention must be adjusted by thickness, material quality or the like such that the shielding means can be ruptured according to the change of the internal pressure in the hybrid inflator. The change of the internal pressure at the actuation of the hybrid inflator varies according to various requirements in application of the hybrid inflator to an air bag system, for example, a mounting position of the air bag in a vehicle interior (for a driver side, a front passenger side, a rear passenger side or the like), a vehicle model, an environmental temperature during use of the air bag system, but it is preferable to use a tape having a thickness of 30 to 300 xcexcm as the shielding means, it is more preferable to use a tape having a thickness of 30 to 80 xcexcm. A material for the tape is not limited to a specific one, but metal, for example, stainless steel or aluminum, is preferable.
The pressurized medium used in the hybrid inflator of the present invention includes an inert gas such as argon, helium (nitrogen is also included in the inert gas in the present invention), etc., and it may contain oxygen as required. Argon promotes thermal expansion of the pressurized medium. It is preferable to contain helium in the pressurized medium since the leakage of the pressurized medium can be detected easily for the purpose of preventing distribution of the imperfect products. Also, oxygen converts carbon monoxide or hydrogen generated due to the combustion of the gas generating agent, serving as the gas generating means, into carbon dioxide or water steam. A charging pressure (=pressure in the inflator housing) of the pressurized medium is preferably 10,000 to 70,000 kpa, and more preferably 30,000 to 60,000 kPa. Incidentally, the pressurized medium may contain oxygen or it may not contain oxygen. When the pressurized medium contains oxygen, the content of oxygen is preferably at most 30 mol %.
As the gas generating means used in the present invention, a gun propellant can be used for example. As the gun propellant, a single-base gun propellant, a double-base gun propellant and a triple-base gun propellant can be used. In addition to them, it is possible to use a gun propellant obtained by mixing a secondary explosive, a bonding agent, a plasticizer and a stabilizer and the like, and molding the resultant mixture to a desired shape.
The secondary explosive can include hexahydrotrinitrotriazine (RDX), cyclotetramethylene tetranitramine (HMX), pentaerithritol tetranitrate (PETN) and triaminoguanidinenitrate (TAGN) . For example, when a gas generating agent using RDX as a secondary explosive is burned in an oxygen-absent atmosphere under a pressure of 20,670 kPa and at a combustion temperature of 3348 K, a formed gas in a combustion gas comprises 33 mol % of nitrogen, 25 mol % of carbon monoxide, 23 mol % of vapor, 8 mol % of carbon dioxide and other gas components.
The bonding agent may include cellulose acetate, cellulose acetate butylate, cellulose acetate propiolate, ethyl cellulose, polyvinyl acetate, azide polymer, polybutadiene, polybutadiene hydride, and polyurethane; the plasticizer may include trimethylolethane trinitrate, butantriol trinitrate, nitroglycerine, bis(2,2-dintropropyl)acetal/formal, glycidyl azide, acetyltriethl citrate, and the like; and the stabilizer may include ethlcentralite, diphenylamine, and loesosinol.
A preferable ratio of the secondary explosive to the bonding agent, plasticizer, and stabilizer is about 50 to 90 wt. % of secondary explosive to about 10 to 50 wt. % of bonding agent, plasticizer and stabilizer in all.
Also, in addition to the above-described gas generating means, as the gas generating means used in the present invention, it is possible to use a gas generating agent including the below described fuel and oxidizer, or the fuel, oxidizer and slag-forming agent, which are mixed with bonding agent, if required, and formed into a desired shape.
It is preferable to use a gas generating agent in a perforated cylindrical shape having at least a single through-hole or non-through-hole (a non-penetrating hole). By using such a perforated cylindrical gas generating agent, combustion of the gas generating agent is promoted, so that operating performance of the hybrid inflator can be improved.
Such a perforated cylindrical gas generating agent can be set properly such that its outer diameter (R), inner diameter (d), and length (L) fall in a range allowing application to the hybrid inflator. In a case of a single-perforated cylindrical gas generating agent having a single through-hole, it is preferable that the outer diameter thereof is 6 mm or less and the ratio (L/W) of the length to the thickness (W) (=(Rxe2x88x92d)/2) is not less than 1. In a case of a porously perforated cylindrical gas generating agent having at least two through-holes, it is preferable that the outer diameter thereof is 60 mm or less and the ratio (L/W) of the length to the thickness (W) (when a plurality of holes are arranged uniformly, a distance between adjacent holes, and when they are not arranged uniformly, the average value of respective distances between adjacent holes) is not less than 1. Furthermore, in a case of a cylindrical gas generating agent with at least a single non-through-hole, it is preferable that the outer diameter thereof is 60 mm or less, the ratio (L/W) of the length to the thickness (W) (the same definition as that in the porously perforated cylindrical one is applied) is not less than 1, and the ratio (Wxe2x80x2/W) of the thickness Wxe2x80x2 (a distance between a bottom portion of the non-through-hole and a bottom of the cylindrical portion) of a non-through-hole portion to the thickness W is 0.5 to 2.
In this gas generating agent, a gas generated by its combustion can be supplied together with the pressurized medium for inflation and development of the airbag. In the present invention, especially, when a gas generating agent including a slag-forming agent is used, the amount of mist discharged from the inflator can be reduced much.
Preferably, the gas generating agent contains a non-azide organic compound except for a nitramine-based compound. The gas generating agent containing the nitramine-based compound may include propellant compositions disclosed in the specification of U.S. Pat. No. 5,507,891 and in claims thereof. For example, it may include compositions containing cyclotrimethylenetrinitramine (RDX) or cyclotetramethylenetetranitramine (HMX). In addition thereto, there are propellants disclosed in JP-A No. 8-282427 and in claims therein. For example, it may include secondary explosive and binders disclosed in Claim 32. The secondary explosive may include RDX, HMX, PETN, TAGN, and the like described in Claim 34 of the Publication, and the binders may include a composition containing a bonding agent such as CA, CAB, CAP, EC, PVA as described in claims 37 and 38.
As the fuel containing the non-azide organic compound except for the nitramine-based compound, the following nitrogen containing compounds may be used. Examples of the fuel can be one or mixture of two or more selected from the group consisting of triazole derivatives, tetrazole derivatives, guanidine derivatives, azodicarboxylic acid amide derivatives, and hydrazine derivatives. Specific examples thereof may include 5-oxo-1,2,4-triazole, tetrazole, 5-aminotetrazole, 5,5-bi-1H-tetrazole, guanidine, nitroguanidine, cyanoguanidine, triaminoguanidine nitrate, guanidine nitrate, guanidine carbonate, burette, azodicarbonamide, carbohydrazide, carbohydrazide nitrate complex, dihydrazide oxalate, hydrazine nitrate complex, and the like.
Preferably, the fuel may be one or two or more materials selected from a group consisting guanidine derivatives such as nitroguanidine (NQ), guanidine nitrite (GN), guanidine carbonate, amino nitroguanicine, amino guanidine nitrite, amino guanidine carbonate, diamino guanidine nitrite, diamino guanidine carbonate, and triamino guanidine nitrite. However, it is not limited thereto.
As an oxidizer, one or two or more materials selected from a group comprising strontium nitrate, potassium nitrate, ammonium nitrate, potassium perchlorate, copper oxide, ferrous oxide, and basic copper nitrate may be used.
Preferable composition amount of oxidizer is 10 to 80 parts by weight, and more preferably, 20 to 50 parts by weight with respect to 100 parts by weight of fuel.
Preferably, the slag-forming agent may be one or two or more materials selected from a group consisting of acid clay, talc, bentonite, diatomaceous earth, kaolin, silica, alumina, sodium silicate, silicon nitride, silicon carbide, hydrotalsite, and a mixture thereof.
Preferable composition amount of slag-forming agent is 0 to 50 parts by weight, and more preferably, 1 to 10 parts by weight with respect to 100 parts by weight of fuel.
Preferably, the bonding agent may be one or two or more materials selected from a group consisting of sodium salt of sodium carboxymethylcellulose, hydroxyethyl cellulose, starch, polyvinyl alcohol, guar gum, microcrystal cellulose, polyacrylamide, and calcium stearate.
Preferable composition amount of the bonding agent is 0 to 30 parts by weight, and more preferably, 3 to 10 parts by weight with respect to 100 parts by weight of fuel.
The present invention can be applied to one (single type) in which a gas generator includes a single gas generating chamber storing a gas generating means, one (dual type) in which the gas generator includes two gas generating chambers, and one in which the gas generator includes three or more gas generating chambers. The arrangement in a case of having two or more gas generating chambers is not limited to a specific one. For example, in a case of having two gas generating chambers, such a structure may be employed that the two gas generating chambers are arranged in series and adjacent to each other in the longitudinal direction, that they are arranged in series but being separated from each other in the longitudinal direction, that they are arranged in parallel and adjacent to each other in the widthwise direction, or that they are arranged in parallel but being separated to each other in the widthwise direction. Incidentally, the case that the gas generating chambers are arranged in parallel to each other in the widthwise direction may include a case such that the two gas generating chambers are arranged concentrically so that either of the gas generating chambers is arranged outside the other, or a case such that the two gas generating chambers each having a widthwise semi-circular section are arranged in the widthwise direction.
In the hybrid inflator of the present invention, the gas generating means may be kept in a normal pressure atmosphere. It is preferable that the gas generating means is kept in the normal pressure atmosphere rather than in a pressurized atmosphere, since the gas generating means hardly deteriorates by pressure. If the gas generating means is deteriorated by the pressure, there is a possibility such that the gas generating means may be smashed easily at combustion.
Further, the present invention provides an air bag apparatus comprising activation-signal outputting means including an impact sensor and a control unit, and a module case which accommodates the above-described hybrid inflator and an air bag.
In the present invention, a xe2x80x9cgas generatorxe2x80x9d functions to generate a high temperature combustion gas due to combustion of the gas generating means (gas generating agent) in the gas generating chamber, thereby introducing the high temperature combustion gas into the inflator housing. And, the hybrid inflator includes the gas generator in an inflator housing thereof, and the xe2x80x9cinflatorxe2x80x9d functions to introduce the pressurized medium, which exists inside of the inflator housing but outside of the gas generator, towards the outside due to a function of the high temperature combustion gas discharged from the gas generator, thereby inflating an inflatable material such as an air bag. The xe2x80x9chybridxe2x80x9d means a combination of the high temperature combustion gas generated by combustion of the gas generating agent and the pressurized medium.
In the hybrid inflator of the present invention, the amount of outflow of the pressurized medium and the combustion gas may be controlled easily so that, when the hybrid inflator is applied to an air bag apparatus, the air bag may be inflated rapidly and reliably without being affected by an environmental temperature.